bug#61667: 29.0.60; Failure to redisplay

[Dmitry Gutov]

On 23/02/2023 00:36, Po Lu via Bug reports for GNU Emacs, the Swiss army 
knife of text editors wrote:
> That won't work, unfortunately -- this needs to check whether or not a function 
> is being called at all, and not just the value of some flags at the time we 
> update the frame title.
>
> This is a bit of a stab in the dark, but: Dimitry, what if you make 
> x_flush_dirty_back_buffer_on return immediately, without performing a buffer 
> flip?

This way, right?

Still repros. :(

diff --git a/src/xterm.c b/src/xterm.c
index e981a36fa9c..aa321e7e3eb 100644
--- a/src/xterm.c
+++ b/src/xterm.c
@@ -17501,6 +17501,8 @@ x_net_wm_state (struct frame *f, Window window)
 x_flush_dirty_back_buffer_on (struct frame *f)
 {
 #ifdef HAVE_XDBE
+  return;
+
   if (FRAME_GARBAGED_P (f)
       || buffer_flipping_blocked_p ()
       /* If the frame is not already up to date, do not flush buffers